Various hot cutting devices are known, which in practice, however, do not fully meet all the technological requirements.
There are known, for example, cutting devices having rigid blades integral with the driving shaft. In such devices, the blade adjustment is difficult and inaccurate, due to the axial rigidity of the complex, and in practice, as it is impossible to obtain a sufficiently uniform behavior of the blades, the consequence thereof is a cut of bad quality and/or a severe wear of the cutting elements.
With a view to overcome these drawbacks, cutting devices having elastic blades or an axially sprung blade-carrying disc have been proposed.
Due to the contact with friction between the blades and the die face, a diffused wear occurs in these devices.
Furthermore, these known cutting devices are not adapted to indiscriminate use with all types of thermoplastic polymers. In fact, the devices having rigid blades are not suitable for relatively soft or low viscosity polymers because, since the blades are to be regulated in a position very close to the die face, in practice there are some areas of irregular contact between the blades and plate, with consequent very severe wear.
Conversely, the cutting devices equipped with elastic blades or with a sprung blade-carrying disc are not suitable for use with polymers of relatively high viscosity and hardness because, since a high thrust of the blades against the plate is necessary, they undergo rapid wear.